1. Preliminary Tests.—-These are made to obtain an idea of the com-
position of the product. The lubricant is first tested to ascertain if it is
completely soluble in ether and in petroleum benzine and if it leaves any
residue when burnt on platinum foil, absence of such residue excluding
the presence of mineral matter and soaps. If it gives with benzene an
opalescent solution, which becomes clear on addition of a little absolute
alcohol, water is present. The smell emitted when the substance is burnt
on platinum foil gives an indication concerning the presence of mineral
oils, resins and fats. If ash is left, a little of the lubricant is treated with
a mixture in equal proportions of petroleum benzine and absolute alcohol,
the liquid being filtered after standing for some hours : the insoluble residue
is investigated for lime and other extraneous mineral substances by the
2. Melting Point.—This is determined empirically and approximately
as follows : The cylindrical bulb of a thermometer is covered with the sub-
stance, without heating, until the shining surface of the mercury is no
longer discernible. The thermometer passes through the stopper of a
test-tube about 18 mm. in diameter, the tube being immersed in a water-
bath which is gradually heated. The temperature at which the substance
begins to melt at the surface and that at which a drop of the fused substance
falls from the thermometer into the tube are noted.
3. Water.—On a boiling water-bath, 3-5 grams of the lubricant are
heated in a tared glass dish with 10-15 c.c. of absolute alcohol, the mass
being stirred until no further frothing occurs and the liquid becomes clear.
When cold, the weight is again taken, the loss representing the moisture.
The latter may also be determined by Marcusson's method (see Crude Petro-
4. Acidity.—As a rule, stiff lubricants contain excess of alkali. When,
however, they exhibit acidity, the latter may be determined as follows
(Marcusson) : 10 grams of the lubricant are heated in a reflux apparatus
with 50-100 c.c. of a neutral mixture of 90 parts of benzine and 10 of 96%
alcohol, any insoluble residue being filtered off in the hot and washed with
the same mixture. The filtrate is mixed with 30 c.c. of 50% alcohol and
the acidity measured by titration in the hot with normal caustic soda in
presence of phenolphthalein.
5. Detection and Determination of Soaps.—From 10 to 12 grams
of the lubricant are shaken vigorously and for a long time, in a 250 c.c.
separating funnel, with 25 c.c. of dilute hydrochloric acid and 50 c-c- °f
ether; on standing, two perfectly clear and well-separated layers should
be formed. Both layers should be tested with litmus paper to make sure
that they are distinctly acid ; if not, more hydrochloric acid must be added
and the liquid again shaken. The hydrochloric solution is then separated
and tested in the ordinary way for bases, especially lime and the alkalies,
which occur in the soaps employed in lubricants.
The ethereal layer separated in the preceding operation ip washed by
shaking with distilled water until neutral, and is then filtered through a
dry filter into a weighed flask of at least 200 c.c. capacity, the separatingin the form of a sticky,